Story By Imma Perfetto | Originally published by Cosmos | In new insight into the effects of artificial underwater structures on marine life, research has found that whale sharks can use oil and gas platforms and other, natural features as migratory “stepping stones” in their journeys.
The findings have implications for the protection of natural features that promote this ability, and for decommissioning platforms.
The undersea pinnacles and seamounts, and oil and gas platforms, offer foraging opportunities and increased prey availability. However, there are also risks for whale sharks associated with oil and gas platforms, such as ship strikes from service vessels and pollutants from discharges and spills.
Whale sharks (Rhincodon typus) are large filter-feeders found throughout the world’s tropical and warm-temperature seas. The study analysed satellite tracking data from 78 whale sharks tagged over 14 years at Ningaloo Reef and Shark Bay off the Western Australian coast.
Their movements were mapped across the eastern Indian Ocean as well as the North West Shelf, an extensive oil and gas region.
“Whale sharks travel huge distances across the oceans,” says Ben D’Antonio, a PhD candidate at the Australian Institute of Marine Science (AIMS) and the University of Western Australia.
“Our study illustrates that they tend to use undersea pinnacles and sea mounts as stepping stones on these journeys because the currents that flow around these features help to enhance food availability like plankton.
“The same is true for the industrial infrastructure found off the north-west coast of Australia. But while seamounts and pinnacles can take up huge areas of up to tens of kilometres across, oil and gas platforms are comparatively small, and yet could provide similar levels of prey availability. There is evidence, for example, that plankton are attracted by the artificial lights on these platforms.”
The findings have implications for decommissioning oil and gas platforms, which may be removed completely or leave behind submerged portions to form artificial habitats.
“The removal of platforms at the end of their productive life may change seascape connectivity by removing migratory stepping stones that link important habitats for whale sharks,” says D’Antonio.
“There is still a need to understand the detail in the relationships between whale sharks and individual oil and gas platforms, like how often and for how long they visit.”
AIMS scientist Dr Luciana Ferreira says the presence of the platforms may also have indirect implications by altering migration patterns and disrupting the movements of whale sharks between natural features.
“There are records of fatal interactions between whale sharks and vessels and a considerable portion of the whale shark population at Ningaloo Reef have scars attributed to vessel strikes,” she says.
“Having said that, whale sharks are at risk across large areas of their distribution from ship strike and fishing bycatch and entanglement, and we need to do more research to better understand the threats.”
The study is published in the journal Diversity and Distributions.
Originally published by Cosmos as Whale sharks have a complicated relationship with oil and gas platforms
